Typically the grounding electrode conductor is fastened to a water pipe or made electrode and extends through an outlet in a service box where it is fastened to a bus bar with a screw.
Exemplary pf prior art ground connectors are as follows:
U.S. Pat. No. 2,710,381 teaches a device for bonding an electric ground wire to an electric outlet or switch box. This apparatus employs a grounding coupling or wedge wherein the electric wire to be connected to the box is placed in a groove and a stud screwed down upon it. A pin having contact with the ground wire also makes contact with the electric outlet box.
U.S. Pat. No. 3,009,128 teaches a coupling nut provided with a terminal connector for use in grounding equipment(not specified). The problem that was solved encompassed making the coupling nuts accessible. Heretofore the coupling nut was attached to the terminal in such a way that after it was in place, the terminal connector was inaccessible or very difficult to access. In the invention the coupling nut is cylindrical, has internal threads for threading to a conduit that projects into a service box. A terminal is mounted outside the fitting and has an opening through which a ground wire from equipment within the box can enter either way, and then a set screw is placed down on the wire either radially or axially.
U.S. Pat. 3,567,843 teaches an electric connector for attaching a waterproof jacketed armored cable to a junction box. The cable is rigidly gripped by the connector, which comprises a resilient grommet surrounding the jacket which is compressed between two threaded members. Stirrups straddle the inner and outer surfaces of the grommet at one end and contact both an exposed metal part of the cable and the connector to provide electric grounding. The connector is also provided with a section extending from the gripping surfaces to thread into the junction box.
U.S. Pat. No. 4,496,791 shows a spring biased connector for electrically bonding a device to a supporting wall. A flanged bushing is threaded into a push button housing mounted on a metal wall. A serrated spring is located between the flange of the bushing and the metal wall so that when the threaded fastener engages the bushing the spring is deflected into the wall and completes an electric circuit. This type of arrangement obviates use of a ground connection wire.
U.S. Pat. No. 5,181,860 teaches a plug and receptacle connector that is to be used on the control box of a machine tool, etc. An earth lug when mounted in an insulator causes a spring piece of the lug to pierce into a chromate film on a galvanized layer of a receptacle shell resulting in conductivity.
As can be seen there are a number of ways of making ground connections; however, none of the above cited grounded connections would satisfy the 1996 National Electrical Code, (hereinafter referred to as Code) which stipulates that a grounding electrode conductor entering a panel board, must be bonded to a metallic surface and must be connected to a grounding electrode, for example a metal water pipe or a metal rod driven into earth. None of the devices mentioned in the above cited patents show such an arrangement. U.S. Pat. No. 2,710,381 bonds an electric ground wire to a metallic box but shows no connection to a grounding electrode. Similarly U.S. Pat. No. 3,567,843 shows electrical grounding of metal surface of a cable to an electrical junction box. In 4,496,791 there are features such as the spring jumper that might be likened to a grounding electrode conductor and the conductive wall might be a grounding electrode; however there is an additional element such as the push button considered to be a grounding conductor. Additionally the conductive wall would not satisfy the code as a ground electrode. As defined in the Code, "Grounding Conductor" is a conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes, that is the push button, mentioned above is the grounding conductor. The "Grounding Electrode Conductor" is the conductor used to connect the grounding electrode to the equipment grounding conductor, to the grounded conductor or to both. The grounding electrode conductor as defined herein provides a low impedance path for service equipment and conductors during fault conditions, short circuits or ground faults. Under normal conditions electricity seeks to return to its source and complete a continuous circuit. This return path is often provided by white neutral wires that return current to the main service panel. A grounding electrode conductor provides an additional return path for electrical current. The ground electrode conductor is a safety feature. As stated above, it is designed to conduct electricity to its source, if current seeks to return to the service panel along a path other than the neutral wire.
Even if the ground wires of the aforesaid patents were to be considered to be grounding electrode conductors they would not satisfy the Code. The fact is that none of the grounding wires is designed to handle an excessive amount of fault current, for example in excess of 10,000 amperes in domestic households, for an extended period of time. This is significant for the reason that if there should be a failure in the circuit and an excessive amount of current is dumped onto this wire, it would be unable to control the situation.
Accordingly it is an object of this invention to provide a grounding electrode conductor to be connected to a panel board that conforms to the 1996 National Electrical Code.
It is another object of this invention to use a grounding electrode conductor that is rated for the available fault current.
It is also another object of this invention to facilitate the securement of the grounding electrode conductor to the panel board by use of a simple clamp.